A model of corneal graft rejection in semi-inbred NIH miniature swine: significant T-cell infiltration of clinically accepted allografts.

PURPOSE: The purpose of our study is to develop a pre-clinical model of corneal graft rejection in the semi-inbred NIH minipig as a model of human rejection. METHODS: NIH minipigs received corneal allografts with MHC and minor mismatches, or minor mismatches alone. Clinical rejection was monitored, and major subsets of leukocytes and ingress of vessels were quantified post-mortem by automated digital methods. Spectratypes of recipient T-cell receptor ß-subunit variable region (TRßV) were analyzed. The capacity of pig corneal endothelial cells to proliferate in vivo was assessed. RESULTS: Autografts (n = 5) and SLA(cc) to SLA(cc) allografts (minor mismatches, n = 5) were not rejected. Median graft survival of SLA(dd) and SLA(bb) allografts in SLA(cc) strain recipients (major and minor mismatches) was 57 (n = 10) and 67 (n = 6) days, respectively. Rejected grafts did not recover clarity in vivo, and corneal endothelial cells did not proliferate in organ culture after cryo-injury. There were significantly more leukocytes in clinically rejected versus accepted grafts (P < 0.0001) and in transplanted versus contralateral eyes (P < 0.0001). Numbers of T-cells were significantly greater in clinically accepted grafts versus autografts and in rejected grafts versus accepted (P < 0.005 for most subsets). There were significant differences in TRßV spectratype between graft groups in cornea, but not in draining lymph node or blood (P < 0.05). CONCLUSIONS: The NIH minipig offers a robust model of human rejection suitable for immunological or therapeutic studies. In particular, there is limited capacity for corneal endothelial repair in vivo, and histological evidence suggests that allosensitization of the recipient may develop in the absence of clinical rejection.

Neonatal colonisation expands a specific intestinal antigen-presenting cell subset prior to CD4 T-cell expansion, without altering T-cell repertoire.

Interactions between the early-life colonising intestinal microbiota and the developing immune system are critical in determining the nature of immune responses in later life. Studies in neonatal animals in which this interaction can be examined are central to understanding the mechanisms by which the microbiota impacts on immune development and to developing therapies based on manipulation of the microbiome. The inbred piglet model represents a system that is comparable to human neonates and allows for control of the impact of maternal factors. Here we show that colonisation with a defined microbiota produces expansion of mucosal plasma cells and of T-lymphocytes without altering the repertoire of alpha beta T-cells in the intestine. Importantly, this is preceded by microbially-induced expansion of a signal regulatory protein α-positive (SIRPα(+)) antigen-presenting cell subset, whilst SIRPα(-)CD11R1(+) antigen-presenting cells (APCs) are unaffected by colonisation. The central role of intestinal APCs in the induction and maintenance of mucosal immunity implicates SIRPα(+) antigen-presenting cells as orchestrators of early-life mucosal immune development.